QPixmapCache#
The QPixmapCache
class provides an application-wide cache for pixmaps. More…
Synopsis#
Functions#
Static functions#
def
cacheLimit
()def
clear
()def
find
(key, pixmap)def
find
(key, pixmap)def
insert
(pixmap)def
insert
(key, pixmap)def
remove
(key)def
remove
(key)def
replace
(key, pixmap)def
setCacheLimit
(arg__1)
Note
This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE
Detailed Description#
This class is a tool for optimized drawing with QPixmap
. You can use it to store temporary pixmaps that are expensive to generate without using more storage space than cacheLimit()
. Use insert()
to insert pixmaps, find()
to find them, and clear()
to empty the cache.
QPixmapCache
contains no member data, only static functions to access the global pixmap cache. It creates an internal QCache
object for caching the pixmaps.
The cache associates a pixmap with a user-provided string as a key, or with a Key
that the cache generates. Using Key
for keys is faster than using strings. The string API is very convenient for complex keys but the Key
API will be very efficient and convenient for a one-to-one object-to-pixmap mapping - in this case, you can store the keys as members of an object.
If two pixmaps are inserted into the cache using equal keys then the last pixmap will replace the first pixmap in the cache. This follows the behavior of the QHash
and QCache
classes.
The cache becomes full when the total size of all pixmaps in the cache exceeds cacheLimit()
. The initial cache limit is 10240 KB (10 MB); you can change this by calling setCacheLimit()
with the required value. A pixmap takes roughly (width * height * depth)/8 bytes of memory.
The Qt Quarterly article Optimizing with QPixmapCache explains how to use QPixmapCache
to speed up applications by caching the results of painting.
Note
QPixmapCache
is only usable from the application’s main thread. Access from other threads will be ignored and return failure.
See also
QCache
QPixmap
- class PySide6.QtGui.QPixmapCache#
- static PySide6.QtGui.QPixmapCache.cacheLimit()#
- Return type:
int
Returns the cache limit (in kilobytes).
The default cache limit is 10240 KB.
See also
- static PySide6.QtGui.QPixmapCache.clear()#
Removes all pixmaps from the cache.
- PySide6.QtGui.QPixmapCache.find(arg__1)#
- Parameters:
arg__1 –
PySide6.QtGui.QPixmapCache.Key
- static PySide6.QtGui.QPixmapCache.find(key, pixmap)
- Parameters:
pixmap –
PySide6.QtGui.QPixmap
- Return type:
bool
Looks for a cached pixmap associated with the given key
in the cache. If the pixmap is found, the function sets pixmap
to that pixmap and returns true
; otherwise it leaves pixmap
alone and returns false
. If the pixmap is not found, it means that the key
is no longer valid, so it will be released for the next insertion.
- PySide6.QtGui.QPixmapCache.find(arg__1)
- Parameters:
arg__1 – str
- static PySide6.QtGui.QPixmapCache.find(key, pixmap)
- Parameters:
key – str
pixmap –
PySide6.QtGui.QPixmap
- Return type:
bool
Warning
This section contains snippets that were automatically translated from C++ to Python and may contain errors.
Looks for a cached pixmap associated with the given key
in the cache. If the pixmap is found, the function sets pixmap
to that pixmap and returns true
; otherwise it leaves pixmap
alone and returns false
.
Example:
pm = QPixmap() if not QPixmapCache.find("my_big_image", pm): pm.load("bigimage.png") QPixmapCache.insert("my_big_image", pm) painter.drawPixmap(0, 0, pm)
- static PySide6.QtGui.QPixmapCache.insert(pixmap)#
- Parameters:
pixmap –
PySide6.QtGui.QPixmap
- Return type:
Inserts a copy of the given pixmap
into the cache and returns a key that can be used to retrieve it.
When a pixmap is inserted and the cache is about to exceed its limit, it removes pixmaps until there is enough room for the pixmap to be inserted.
The oldest pixmaps (least recently accessed in the cache) are deleted when more space is needed.
See also
- static PySide6.QtGui.QPixmapCache.insert(key, pixmap)
- Parameters:
key – str
pixmap –
PySide6.QtGui.QPixmap
- Return type:
bool
Inserts a copy of the pixmap pixmap
associated with the key
into the cache.
All pixmaps inserted by the Qt library have a key starting with “$qt”, so your own pixmap keys should never begin “$qt”.
When a pixmap is inserted and the cache is about to exceed its limit, it removes pixmaps until there is enough room for the pixmap to be inserted.
The oldest pixmaps (least recently accessed in the cache) are deleted when more space is needed.
The function returns true
if the object was inserted into the cache; otherwise it returns false
.
See also
- static PySide6.QtGui.QPixmapCache.remove(key)#
- Parameters:
Removes the pixmap associated with key
from the cache and releases the key for a future insertion.
- static PySide6.QtGui.QPixmapCache.remove(key)
- Parameters:
key – str
Removes the pixmap associated with key
from the cache.
- static PySide6.QtGui.QPixmapCache.replace(key, pixmap)#
- Parameters:
pixmap –
PySide6.QtGui.QPixmap
- Return type:
bool
Replaces the pixmap associated with the given key
with the pixmap
specified. Returns true
if the pixmap
has been correctly inserted into the cache; otherwise returns false
.
See also
- static PySide6.QtGui.QPixmapCache.setCacheLimit(arg__1)#
- Parameters:
arg__1 – int
Sets the cache limit to n
kilobytes.
The default setting is 10240 KB.
See also